A. Field of the Invention
The present invention relates to a novel device that provides a hands-on method to observe and record the time-varying temperature distribution within a heat-conducting body, such as a metal plate, using thermocouples and thermochromic liquid crystal sheet. The invention has applications for use in teaching students about transient heat conduction.
B. Description of the Related Art
Thermochromic liquid crystals (xe2x80x9cTLCsxe2x80x9d) are organic long-chain molecules that have the useful property of being temperature sensitive. They respond to temperature by changing their molecular structure. The change in molecular structure causes changes in the wavelength of light that is reflected by the TLCs. The result is that the TLCs will change color in response to temperature. Contrary to conventional color representation of temperatures, TLCs will display a red color at low temperatures and a blue color at higher temperatures. During the transition from lower to higher temperatures, TLCs will display a spectrum of colors. TLCs are described in detail in U.S. Pat. No. 4,741,859, titled xe2x80x9cThermochromic liquid crystal materials and devicesxe2x80x9d, issued May 1988, the disclosure of which is herein incorporated by reference.
TLCs are typically described with two criteria: (1) red start; and (2) color bandwidth. These criteria are commonly defined using degrees Celsius (xc2x0 C.) values. Red start is the temperature at which color play commences. Color bandwidth is the temperature range over which the colors change from red to blue. TLCs can be obtained from various manufacturers with customized red start and color bandwidth values. TLCs can be in either a slurry form that can be added to a liquid flow, or in the form of a sheet. Common uses for TLCs are thermometers for aquariums and battery tester strips.
In teaching students the concept of heat conduction, the inventors have found that an apparatus capable of visually and electronically documenting the transient temperature changes in a heat-conducting body is an excellent tool. Thus, the present invention is directed towards such an apparatus and the method of using the apparatus in a student teaching exercise.
The present invention provides an apparatus to observe transient heat conduction in a heat-conducting body. The heat-conducting body can be in the form of a cube, plate, sphere or nearly any other form. The apparatus of the present invention may be used in a process to study one, two, or three dimensional heat flow in a teaching laboratory exercise. The invention is well-suited for use in schools to give students a hands-on experience with transient heat conduction. The present invention combines the results obtained from the teaching exercise using the apparatus with a numerical simulation of the transient heat conduction within the heat-conducting body of the apparatus and have the students make a comparison of the actual results with the numerically-simulated results.
Additional advantages of the invention will be set forth in part in the description which follows, and in part will be learned from the description, or may be learned by practice of the invention. The advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.
In accordance with the purpose of the invention, as embodied and broadly described herein, the invention comprises a heat-conducting body that is heated on at least one surface and cooled on at least one surface. Within the heat-conducting body is a means to measure temperature, such as a plurality of thermocouples. Additionally, at least one surface of the heat-conducting body has a means to visually observe the temperature of the heat-conducting body, such as a sheet or covering of thermochromic liquid crystals (xe2x80x9cTLCsxe2x80x9d). A visual recordation means, such as a color charge-coupled device (CCD) camera, records the transient temperature changes displayed by the visual observation means to visually observe and record the temperature of the heat-conducting body.
In conducting the teaching laboratory experiment, the transient temperature changes within the heat-conducting body are observed using the output of both the means to measure temperature and the means to visually observe temperature. In a preferred embodiment of the invention, the means to measure temperature is performed by observing the transient output of the thermocouple array within or upon the heat-conducting body. Additionally, the transient temperature changes are observed using the means to visually observe temperature. In a preferred embodiment of the invention, the color changes of the TLC are observed. Use of the visual recordation means allows for a comparison of the observations of the means to measure temperature and the means to visually observe the temperature. A final exercise in the teaching laboratory is to compare the results obtained with the means to measure temperature and the means to visually observe temperature with a numerical simulation of the heat-conducting body.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.